If I start a workout using the app on iPhone, my phone’s performance will slow to a crawl. If I switch to a different app while the workout is running in the background with all of the rest timers, it will just slow my phone down dramatically. There have been multiple instances where I have to turn off my phone completely MULTIPLE times to clear the app from using all that memory.

I won’t use the phone app anymore to track workouts. I only use the Apple Watch version.